Sameer Jafri
Sameer Jafri
Importance of Time-to-Defibrillation

Sudden Cardiac Arrest and its Treatments

Sudden Cardiac Arrest (SCA) refers to when the heart suddenly and unexpectedly stops. Without a functional heartbeat, blood and oxygen are unable to reach the brain and other vital organs. Ventricular fibrillation (VF), in which the ventricles (heart’s lower chambers) lose their normal rhythm, is the most common way that SCA manifests itself. Ventricular tachycardia (VT), another form of SCA characterized by fast, irregular heartbeats is less common but is also extremely dangerous. SCA is brought about by many factors including ischemic heart disease, intense physical stress, lifestyle-related problems that may alter heart structure, and various hereditary disorders. 

Without quick intervention, SCA typically leads to death within minutes. Fewer than 11% of people who experience SCA survive to hospital discharge and it is one of the leading causes of death in the United States. According to statistics from the American Heart Association, out-of-hospital SCA took the lives of 356,000 people in 2018.

During Sudden Cardiac Arrest, electrical defibrillation, a process that involves sending a special kind of electric “shock” through the heart, is the most effective way to reestablish a normal, functional heartbeat. Although cardiopulmonary resuscitation (CPR) cannot restart the heart like defibrillation, CPR can help increase the odds of survival and should be applied immediately.

Importance of Time-to-Defibrillation

Time-to-defibrillation refers to the length of time between the onset of Sudden Cardiac Arrest in a patient and the first attempt at defibrillation. Time-to-defibrillation is essentially a measure of how quickly first responders administer treatment to patients during SCA emergencies. Early defibrillation is a critical determinant of survival, particularly in VF-related SCA. In the “chain of survival,” which involves a series of four steps that are needed for successful SCA resuscitation, early defibrillation is the most important link. Since defibrillation is the most effective treatment for VF cardiac arrest, the longer a patient has to wait for a defibrillation shock, the lower the chances of survival. Although cardiologists say that CPR can prolong the neurological viability of a patient in VF for as long as ten minutes using chest compressions, CPR alone cannot restore a normal rhythm and defibrillation is required to regain heart function.

 

The survival rate from SCA decreases between 7 and 10 percent for every minute that the patient has to wait for defibrillation

Automated External Defibrillators Decrease Time-to-Defibrillation

Automated External Defibrillators (AED) are small, portable defibrillators designed mainly for out-of-hospital settings. The device, which was developed in 1973, consists of computer circuitry, batteries, and capacitors that enable it to measure cardiac rhythm and deliver shock therapy to patients in cardiac arrest. AEDs are often placed in public places such as malls, swimming pools, police cruisers, airplanes, and homes for use by both Emergency Medical Services (EMS) personnel and trained laypersons. Different AEDs have varying levels of capability. These range from pure shock-inducing AEDs, semi-automatic varieties, to fully automated systems that diagnose the heart rhythm and deliver the shock automatically if needed.

Commonly, the time-to-defibrillation is dependent on how quickly EMS personnel can get to the scene of an emergency and use their advanced equipment. With an AED, however, first responders such as firefighters and police officers, or even minimally trained bystanders and family members, can rapidly administer defibrillation and thus improve the prognosis of the patient. Aside from their simplicity, AEDs are designed with safety in mind, so that even errors in an application do not result in harm to the patient or person administering the shock.

Increasing the number of AEDs that are publically available has been one of the recommendations/requirements that many health authorities in the industrialized world have instituted. In the United States, over 200,000 AEDs are sold every year. In many of the areas where AEDs have been made available, there has been a significant reduction in the time-to-defibrillation and, thus, an improvement in SCA survival rates. A study of casinos where security personnel and on-ground medical personnel had AEDs found that the mean time to defibrillation was 2.9 minutes whereas paramedics take an average of 9.8 minutes to arrive.

 

Time-to-Defibrillation and SCA Survival Rates

Faster response times are associated with a greater likelihood of SCA survival, making AEDs critical in remote or congested places where EMS response times are slower. Various studies have found a correlation between survival rates from SCA and the use of AEDs.

Medical experts recommend that defibrillation be attempted as quickly as possible after the onset of cardiac arrest because survival from VF is determined primarily by the time-to-defibrillation. According to the American Heart Association, the survival rate from SCA decreases between 7 and 10 percent for every minute that the patient has to wait for defibrillation.

“Relation of collapse to CPR and defibrillation to survival: simplified model. Graphical representation of simplified (includes collapse to CPR and collapse to defibrillation only) predictive model of survival after witnessed, out-of-hospital cardiac arrest due to VF. Each curve represents change in probability of survival as delay (minutes) to defibrillation increases for a given collapse-to-CPR interval (minutes).”

– Valenzuela TD, Et al.

Out-of-Hospital SCA

A study involving 13,769 out-of-hospital cardiac arrests found that survival rates to hospital discharge were 7% with no form of resuscitation attempt, 9% when only CPR was performed and 38% when AED shock therapy was given.

Another study of 105 patients whose initial rhythm was VF, the survival rate was 74% for those who received their first defibrillation no later than three minutes after the witnessed collapse and 49% for those who received their first defibrillation three minutes after the witnessed collapse.

In a closely related experimental study conducted in the Piacenza region of Italy, researchers provided 1285 lay volunteers with 39 AEDs. The volunteers, who had no traditional training in CPR responded to all reported cases of SCA alongside regular EMS over a period of 22 months during which important metrics were recorded. The volunteers handled 143 SCA cases, including un-witnessed and non-shockable SCA, registering an average arrival time of 4.8 minutes compared to 6.2 minutes for regular EMS. More importantly, the survival to hospital discharge rate for patients attended to by the volunteers was three times higher than with EMS intervention (10.5% versus 3.3%).

These research statistics, as well as a vast wealth of anecdotal evidence, underline the critical role that AEDs have to play in the management of SCA. They are cost-effective, safe, and research has shown them to improve survival rates in the most critical locations where emergency services take longer to respond. 

References:

  1. American Heart Association, “What Is an Automated External Defibrillator?”, Heart.Org, accessed 16 February 2019, https://www.heart.org/-/media/data-import/downloadables/pe-abh-what-is-an-automated-external-defibrillator-ucm_300340.pdf.
  2. John P. Marenco et al., “Improving Survival from Sudden Cardiac Arrest”, JAMA 285, no. 9 (2001): 1193, doi:10.1001/jama.285.9.1193.
  3. The American Heart Association. “The Heart Disease and Stroke Statistics – 2013 Update” January 31, 2018. Circulation. 2018;137:e67–e492.
  4. The American Heart Association. “The Heart Disease and Stroke Statistics – 2013 Update
  5. American Heart Association, “Part 4: The Automated External Defibrillator: Key Link In The Chain Of Survival”, Circulation 102, no. 1 (2000): I-60-I-76, doi:10.1161/01.cir.102.suppl_1.i-60.
  6. Rea and Page, “Community Approaches to Improve Resuscitation After Out-Of-Hospital Sudden Cardiac Arrest.”.
  7. American Heart Association, “What is an Automated External Defibrillator?”
  8. Marenco et al., “Improving Survival From Sudden Cardiac Arrest.”
  9. American Heart Association, “Part 4: The Automated External Defibrillator: Key Link in The Chain of Survival.”
  10. American Heart Association, “What is an Automated External Defibrillator?”
  11. Rea and Page, “Community Approaches to Improve Resuscitation After Out-Of-Hospital Sudden Cardiac Arrest.”.
  12. Myron L. Weisfeldt et al., “Survival After Application Of Automatic External Defibrillators Before Arrival Of The Emergency Medical System”, Journal Of The American College Of Cardiology 55, no. 16 (2010): 1713-1720, doi:10.1016/j.jacc.2009.11.077.
  13. Marenco et al., “Improving Survival from Sudden Cardiac Arrest.”
  14. Valenzuela TD, Roe DJ, Cretin S, Spaite DW, Larsen MP. Estimating effectiveness of cardiac arrest interventions: a logistic regression survival model. Circulation1997;96:3308-3313
  15. American Heart Association, “Part 4: The Automated External Defibrillator: Key Link in The Chain of Survival.”
  16. Valenzuela TD, et al. “Estimating effectiveness of cardiac arrest interventions: a logistic regression survival model.”
  17. Weisfeldt et al., “Survival After Application of Automatic External Defibrillators Before Arrival of the Emergency Medical System.”
  18. Terence D. Valenzuela, M.D., M.P.H. et al., “Outcomes of Rapid Defibrillation by Security Officers after Cardiac Arrest in Casinos” N Engl J Med 2000; 343:1206-1209
  19. A. Cappuci, D. Aschieri and M.F. Piepoli, “Tripling Survival from Sudden Cardiac Arrest Via Early Defibrillation Without Traditional Education in Cardiopulmonary Resuscitation”, ACC Current Journal Review 12, no. 1 (2003): 71-72, doi:10.1016/s1062-1458(02)01052-8.
  20. Cappuci, Aschieri and Piepoli, “Tripling Survival from Sudden Cardiac Arrest Via Early Defibrillation Without Traditional Education in Cardiopulmonary Resuscitation.”

Contact Us

We would love to hear from you!